Fulvestrant 500 Mg as First-Line Treatment in Hormone-Positive (HR+) Metastatic Breast Cancer (MBC) Patients (PTS): Prospective Evaluation of Activity, Safety, Quality of Life (QOL) and Tumour Markers Changes

ABSTRACT Background Fulvestrant 500 mg has been shown to have a biologically greater effect and to produce a clinical meaningful benefit over Fulvestrant 250 mg. We carried out a prospective phase II trial to evaluate the activity and safety of such an option as 1st line treatment of HR+ MBC; an analysis of QoL, patient compliance, and prognostic value of tumour markers monitoring was also performed. Patients and methods Pts with HR+ MBC relapsing after Tamoxifen and/or Aromatase Inhibitors adjuvant therapy received Fulvestrant 500 mg i.m. on day 0, then 500 mg on days 14-28 and every 28 days thereafter, until disease progression or unacceptable toxicity or patient refusal. Changes in cancer antigen 15.3 (CA 15.3) and carcinoembryonic antigen (CEA) were monitored monthly over treatment; QoL and treatment tolerability were assessed every 2 cycles. Results Forty-eight consecutive pts were enrolled and treated. The overall clinical benefit rate was 68%, with 3 (6%) complete (CR) and 12 (25%) partial responses (PR), and 18 (48%) stable diseases (SD ) lasting >24 weeks. The median PFS was 11 months, median response duration was 9 months. Toxicity was manageable, also in pts given long-duration therapy (>18 months). Analysis of QoL by QLQ-BR23 showed no deterioration of the evaluated items over treatment, while the compliance assessment documented an improvement of tolerability of treatment compared with their previous adjuvant hormonotherapy. In pts achieving a CR or PR both CA 15.3 and CEA serial levels decreased significantly over the first 4 months of treatment, while in long-lasting SD a statistically significant difference from baseline was reached within a median of 8 months. Conclusions Our results confirm the known activity and tolerability of Fulvestrant 500 mg as 1st line therapy for HR+ MBC, with good patient compliance over long-term treatment and preservation of QoL. Of interest, changes in tumour markers resulted significantly predictive of treatment activity in responding pts, in contrast with previously reported data with Fulvestrant 250 mg, reflecting and additional difference between the two drug dosages. Disclosure All authors have declared no conflicts of interest.